1. Field of Invention
The present invention relates to a new and improved device for detecting the unbalance in rotating machines, especially in aircraft jet engines, from a threshold considered to be detrimental to the safety of personnel or to the length of life of the machine.
2. Brief Description of Prior Art
Kalb U.S. Pat. No. 2,303,474 discloses a mercury switch device "having an electromagnetic armature operable in a reciprocating movement".
Beckman U.S. Pat. No. 3,034,043 discloses an frequency selective device driven by a piezoelectric transducer and protected by a shock responsive switch which utilizes a "bead or drop of cohesive or elastic electrically conductive material such as mercury".
Green U.S. Pat. No. 3,973,095 discloses a resonating mercury switch, set at the 9000 Hz. frequency of braking glass "to resonate, causing the mercury to overcome the slight flow resistance due to contact with the electrode, the platinum spike, and the glass, and migrate toward the electrode".
Bollen U.S. Pat. No. 4,329,670 discloses an "mercury switch operating in the so-called Form C mode".
Powell U.S. Pat. No. 4,279,159 discloses a vibration monitoring device that utilizes a piezoelectric accelerometer.
Sakurada U.S. Pat. No. 4,441,370 discloses an improvement in the manufacturing of cantilever type vibration sensors by substantially eliminating the disadvantages and inconveniences inherent in prior art.
Maguire U.S. Pat. No. 4,455,461 discloses a imbalance detector that utilizes a pendulum arm that is tuned to a critical frequency.
Anderson U.S. Pat. No. 4,463,610 & 4,479,389 discloses a vibration detector that utilizes a magnetostrictive element and a detecting means.
Wilder U.S. Pat. No. 4,665,393 discloses a vibration monitoring system that utilizes a probe element in spaced relation to the shaft for contact therewith upon occurrence of excessive vibration.
Miyamoto U.S. Pat. No. 4,751,848 discloses a vibration sensor that utilizes an electrically conductive elastic material with its conductivity variable according to a strain thereof produced by the resonant vibration.
Serveau U.S. Pat. No. 4,910,502 discloses a device for detecting unbalance by a pendulum formed from a vertical rod made of an elastically deformable metal.
Brand U.S. Pat. No. 5,001,933 discloses a micromechanical vibration sensor utilizing a conductive cantilevered beam and an integrated circuit and microchip.
Ubukata U.S. Pat. No. 5,021,618 discloses a acceleration responsive switch that utilizes an electrically conductive liquid such as mercury and a pair of electrodes which are brought in contact with the conductive liquid when a shock acting on the receptacle causes the conductive liquid to move.